# Solid Mechanics

## Research Samples

Student:  Prithvi Akella
Mentor:  Evan Hemingway

Research Project Title:  Analysis of Static and Dynamic Beam Deformation through Euler-Bernoulli and Timoshenko Beam Theories.

Abstract:My research details the theory behind both Euler-Bernoulli and Timoshenko beam deformation for both the static and vibrational cases. This document is meant to be used in conjunction with its accompanying Mathematica code to help inform the user about beams deform in general. The first half of my paper will describe Euler-Bernoulli beam theory and attempt to reference the code whenever possible to as to make the gist of the code clear; the second half will proceed likewise with Timoshenko Beam Theory. That being said, while this document will reference the code, it may be used standalone to understand either theory as well.

Student: Nicholas Corral
Mentor: James Urban
Research Project Title: The flaming ignition of aluminum particles.

Abstract:
The increasing rates of unplanned fires in both wild and urban settings, especially in the Western portion of the United States, has brought about the need for research concerning the cause of such tragic events. This research project specifically concerns the effects of spot fire ignition on characteristic combustible materials, and modeling them.The grinding or cutting of metal can create metal sparks which can chemically react with the oxygen in the atmosphere. This can cause an increase in their temperature which makes them a potential source for ignition. In the Combustion Fire Processes Laboratory, a computational model has been developed to simulate the reaction process and the distances these sparks travel. This involves solving the equations of motion and the heat and mass transfer to and from the particle. By making models like this, the fire risk posed by metal cutting and other spark producing processes can be better evaluated preventing dangerous and costly fires.

The ignition of combustible material by hot metal particles is an important pathway by which wildland and urban spot fires are started. Upon impact with combustible material (e.g. vegetation, cellulosic industrial material or polymer foams), these particles can initiate spot fires. In spite of interest in the subject, there is little work published that addresses the ignition capabilities of hot metal particles landing on natural fuels. This work is an experimental study of how the flaming ignition propensity of fuel beds in contact with hot aluminum particles is affected by the characteristics of the fuel bed. Two fuel beds were tested: pine needles and a fine powder formed by grinding the pine needles which are representative of forest litter and duff respectively. Comparing the ignition characteristics of these fuels will give insight into the effects of fuel macrostructure on the conditions which could initiate spot fires from metal particles. Thus, influential variables are monitored through frequent sampling such as the fuel bed moisture content and lab conditions (e.g. temperature, humidity, etc.). In the experiments, aluminum particles ranging from 2 – 8mm in diameter are heated to various temperatures between 575 – 1100oC and dropped into the different fuel beds.

I conducted, acquired, and analyzed the data for the various experiments used in the presentation of the spot project. The various parameters such as the particle diameter, temperature, particle ignition, etc. were recorded after every run of the experiment. The tests also involved constant moderation to keep the particles from melting within the furnace and therefore the real-world imitation for these tests became a bit less accurate than for others. Afterward, I would assist James by writing code in Jupyter/Python to visualize the results and improve the speed of the calculations. The results show that the pine needle powder fuel was capable of ignition at lower temperatures, but the flame spread faster on the pine needle fuels. As for the pine straw grass and powder, fire ignition seldom occurred even with large particles and smolder occurred just as infrequently.

Student:  Thomas Mackey
Research Project Title:  Computer Simulation of Hip Fracture

Abstract

Around 200,000 cases of hip fracture occur in the United States each year, however the mechanics of what causes these hip fractures are not well understood. In particular, 90% of hip fractures are the result of falls, yet it is difficult to see how variables such as angle of impact, impact speed, muscle properties etc. affect the stress distribution in the hip. Woochol Joseph Choi and Stephen N. Robinovitch conducted research on how both muscle activation and the angle of impact affect the force, moments and stress in the hip. While their research determined that “increases in muscle force were protective (caused a reduction in bending moment, and peak compressive and tensile stress) at zero degree and anterior impact angles, and dangerous (caused an increase in bending moment and peak stresses) for posterior impact angles” certain limitations on their research study could cause uncertainty and inaccuracy in their results. Particularly, they modeled the muscle forces as point loads which we believe could significantly increase the amount of stress experienced in the hip. We feel that by simulating the muscle forces as distributed loads we will see much lower peak stresses than that obtained from their research. In addition, the model of soft tissue used was symmetric with respect to angle of impact, and thus not representative of real world scenarios. We feel that by using ANSA and LS Dyna to model the complex geometry of the soft tissue, we can see if the extra cushioning in the posterior negates the increased stress caused by muscle activation. Choi and Robinovich also only tested the impact at one specific location, we would like to see if their results hold true for other locations of impact. Finally in Choi and Robinovich’s paper only 7 different angles were tested. In order to have a better understanding of the relationship between angle of impact and stress in the hip we wanted to test more angles.

Area:  Mechanics
Student:  Charlene Shong